Method and device for reconstructing and compensating magnetic field noise based on in-situ measurement of quantum system

Abstract

The application provides a magnetic field noise reconstruction and compensation method and device based on in-situ measurement of a quantum system, and relates to the technical fields of quantum state measurement, noise measurement and suppression, quantum information processing and the like; the magnetic field noise reconstruction and compensation method comprises the following steps: S1: performing a predetermined measurement sequence based on a quantum system to measure a quantum state; S2: acquiring a measurement result of quantum state evolution under the influence of magnetic field noise; S3: reconstructing a characteristic parameter of the magnetic field noise in real time based on the measurement result; S4: generating compensation information according to the characteristic parameter; and S5: compensating the magnetic field noise with time-varying characteristics based on the compensation information.

Description

Technical Field

[0001] This invention relates to the fields of quantum state measurement, noise measurement and suppression, and quantum information processing, and particularly to a method and apparatus for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems. Background Technology

[0002] In sophisticated quantum experimental systems such as ion traps, ambient magnetic field noise can cause frequency shifts and decreased coherence of qubit transitions. In particular, alternating magnetic field noise generated by the slow drift of the bias magnetic field and the mains frequency (50Hz / 60Hz) and its harmonic components often persists throughout the experiment, significantly impacting the stability and repeatability of the results. Therefore, how to acquire and suppress magnetic field noise in the experimental environment in situ has always been a crucial technical challenge in quantum experimental systems.

[0003] To address the aforementioned issues, various magnetic field stabilization and compensation schemes have been proposed in existing technologies, which can be mainly divided into the following three categories: The first category employs passive magnetic field stabilization methods, such as setting up magnetic shielding structures (e.g., permalloy shielding) around the experimental setup, or selecting atomic transition forms that are insensitive to first-order magnetic field changes (e.g., magnetic field-insensitive states), to reduce the coupling strength of environmental magnetic field fluctuations to the quantum system. This type of scheme typically relies on high-performance magnetic shielding materials and precise device structure design. The second category uses external magnetic field detection units (e.g., fluxgate magnetometers, atomic magnetometers) to measure the experimental environment's magnetic field, and generates a reverse magnetic field through compensation coils based on the detection results to achieve active feedback compensation of magnetic field noise. This type of scheme can acquire certain environmental magnetic field information and improve magnetic field stability under certain experimental conditions. The third category introduces the quantum system's own response to magnetic field noise as a reference signal, achieving magnetic field noise sensing and compensation control through the measurement results of the qubits, aiming to more directly reflect the magnetic field changes experienced by the qubits.

[0004] However, the above-mentioned existing technical solutions still have many major problems in practical applications, such as: (1) Insufficient measurement non-in-situ and spatial representativeness: The installation position of the external magnetic field detection unit is spatially separated from the actual location of the quantum system. When the number, working status or spatial distribution of electrical equipment in the laboratory changes, the magnetic field noise characteristics at different spatial locations may be significantly different, making it difficult for the magnetic field measurement results at the detection position to represent the actual magnetic field environment of the quantum bit location. At this time, there may be a situation where the magnetic field stability at the detection position is good, but the improvement of the coherence performance of the quantum bit is limited. At the same time, the hysteresis and remanence effects of the magnetic shielding material may also introduce low-frequency magnetic field changes, further affecting the measurement accuracy. (2) Limited measurement bandwidth and introduction of additional noise: Due to the limitations of the bandwidth, sensitivity and anti-interference ability of the magnetic field detector itself, the existing magnetic field detection unit is usually difficult to perform high-precision, real-time measurement of magnetic field noise in a wide frequency band; the detection circuit and its connection lines are easily affected by the coupling interference of environmental electromagnetic radiation, thus introducing additional noise unrelated to the environmental magnetic field into the measurement signal. In addition, traditional quantum measurement methods are also limited in terms of measurement bandwidth and timing flexibility, making it difficult to simultaneously cover low-frequency drift and high-frequency alternating magnetic field noise. (3) Strong dependence on initial conditions and environment: Although the third type of scheme can directly reflect the response of atoms to magnetic field noise, the existing schemes generally have high requirements for the initial coherence time of the experimental device, the level of environmental magnetic field noise and the initial state of the system, making it difficult to achieve universal magnetic field noise measurement and compensation under complex experimental conditions.

[0005] In summary, existing magnetic field stabilization and compensation methods generally suffer from problems such as non-in-situ measurement processes, insufficient spatial representativeness, limited measurement bandwidth, and strong dependence on initial experimental conditions and environment. These make it difficult to achieve accurate, stable, and universally applicable magnetic field noise measurement and compensation under complex experimental conditions. Summary of the Invention

[0006] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a method and apparatus for magnetic field noise reconstruction and compensation based on in-situ measurement of a quantum system. This method eliminates the need for external magnetic field detection devices, directly utilizing the measurement results of qubits to obtain magnetic field noise information. This addresses the problem of existing magnetic field stabilization schemes being heavily dependent on the position of external probes, environmental conditions, and the initial state of the system, thereby improving the applicability and versatility of the magnetic field stabilization scheme. The technical solution is as follows:

[0007] According to one aspect of the present invention, a method for reconstructing and compensating magnetic field noise based on in-situ measurement of a quantum system is provided, comprising the following steps: S1: performing a predetermined measurement sequence based on the quantum system to measure the quantum state; S2: obtaining the measurement results of the quantum state evolution under the influence of magnetic field noise; S3: reconstructing the characteristic parameters of the magnetic field noise in real time based on the measurement results; S4: generating compensation information based on the characteristic parameters; S5: compensating for the time-varying magnetic field noise based on the compensation information.

[0008] According to embodiments of the present invention, when reconstructing the characteristic parameters of magnetic field noise, a spectrum analysis or model estimation method is used. The characteristic parameters include the amplitude, phase, frequency components, or spectrum distribution of the magnetic field noise.

[0009] According to an embodiment of the present invention, a spectral analysis method is used to reconstruct the characteristic parameters of magnetic field noise. The frequency domain analysis is performed on the measurement data sequence containing time information to extract the spectral characteristics of magnetic field noise, thereby realizing the real-time reconstruction of the characteristic parameters of magnetic field noise.

[0010] According to an embodiment of the present invention, a model estimation method is used when reconstructing the characteristic parameters of magnetic field noise. A parameterized physical model is constructed based on the dynamic characteristics of magnetic field noise, and Bayesian estimation method, recursive filtering method or adaptive filtering method is used to reconstruct the characteristic parameters of magnetic field noise in real time in combination with the measurement results.

[0011] According to embodiments of the present invention, when compensating for magnetic field noise with time-varying characteristics, a phase compensation method based on quantum manipulation pulse parameter adjustment or an opposite magnetic field compensation method is adopted.

[0012] According to an embodiment of the present invention, the phase compensation method based on quantum manipulation pulse parameter adjustment includes: calculating the phase accumulation caused by magnetic field noise in the measurement sequence; and adjusting the phase and / or rotation angle in the quantum manipulation pulse parameters based on the phase accumulation.

[0013] According to an embodiment of the present invention, when using the opposite magnetic field compensation method, a compensation magnetic field opposite to the magnetic field noise is generated by controlling the magnetic field compensation device. The magnetic field compensation device includes a single-axis Helmholtz coil structure, and the direction of the compensation magnetic field is along the quantization axis direction, so as to achieve compensation for the magnetic field noise in the quantization axis direction.

[0014] According to embodiments of the present invention, the quantum system is an ion trap system, a neutral atom system, a color center system, or a superconducting quantum bit system.

[0015] According to embodiments of the present invention, the measurement sequence includes a Ramsey interferometry sequence, a spin echo sequence, or a dynamic decoupling sequence; the measurement result is a measurement data sequence containing time information.

[0016] In another embodiment of the present invention, a magnetic field noise reconstruction and compensation device based on in-situ measurement of a quantum system is provided, comprising a quantum system, a data acquisition module, a parameter reconstruction module, a compensation generation module, and a compensation execution module.

[0017] The quantum system is configured to perform a predetermined measurement sequence to measure the quantum state; the data acquisition module is configured to acquire the measurement results of the quantum state evolution under the influence of magnetic field noise; the parameter reconstruction module is configured to reconstruct the characteristic parameters of the magnetic field noise in real time based on the measurement results; the compensation generation module is configured to generate compensation information based on the characteristic parameters; and the compensation execution module is configured to compensate for the time-varying magnetic field noise based on the compensation information. Attached Figure Description

[0018] The objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0019] Figure 1 This is a flowchart illustrating the magnetic field noise reconstruction and compensation method based on in-situ measurement of a quantum system, according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of a magnetic field noise reconstruction and compensation device based on in-situ measurement of a quantum system, according to an embodiment of the present invention. Detailed Implementation

[0021] This invention provides a method and apparatus for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems, applicable to magnetic field noise measurement and compensation of single-qubit systems. The method uses the atoms themselves in the quantum system as magnetic field-sensitive elements. By analyzing the correlation between quantum state measurement results and time information, it obtains the characteristics of environmental magnetic field noise and generates a compensation signal accordingly, thereby reducing the impact of magnetic field noise on the coherence of the quantum system. The process is executed cyclically according to the steps of measurement → reconstruction → compensation → re-measurement, forming a closed-loop magnetic field noise compensation process.

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] In this embodiment of the invention, a method for reconstructing and compensating magnetic field noise based on in-situ measurements of a quantum system is provided, such as... Figure 1 As shown, the magnetic field noise reconstruction and compensation method includes the following steps:

[0024] S1: Execute a predetermined sequence of measurements based on the quantum system to measure the quantum state;

[0025] S2: Obtain the measurement results of quantum state evolution under the influence of magnetic field noise;

[0026] S3: Real-time reconstruction of characteristic parameters of magnetic field noise based on measurement results;

[0027] S4: Generate compensation information based on feature parameters;

[0028] S5: Compensate for time-varying magnetic field noise based on compensation information.

[0029] According to an embodiment of the present invention, the quantum system is an ion trap quantum experimental system, which contains at least one atom or ion as a qubit, whose transition frequency is sensitive to changes in the external magnetic field. Magnetic field noise mainly originates from the drift of the bias magnetic field in the laboratory environment and the alternating magnetic field disturbance caused by the mains frequency and its harmonic components. The quantum system can be, for example, an ion trap system, a neutral atom system, a color center system, or a superconducting qubit system. The quantum system performs a predetermined measurement sequence to measure the quantum state, obtaining measurement results (measurement data sequence) reflecting the quantum state evolution under the influence of magnetic field noise, including corresponding measurement time information. The measurement sequence can be, for example, a Ramsey interference sequence, a spin echo sequence, or a dynamical decoupling sequence; the measurement result is a measurement data sequence containing time information.

[0030] In the technical solution of the magnetic field noise reconstruction and compensation method and device based on in-situ measurement of quantum system of the present invention, no magnetic field detection device independent of quantum system is set up. The acquisition and characterization of magnetic field noise is completed entirely based on the measurement results of quantum system itself, thereby realizing the in-situ characterization of magnetic field noise actually felt by atoms.

[0031] According to an embodiment of the present invention, based on the measurement results, the characteristic parameters of the magnetic field noise are reconstructed using spectral analysis or model estimation methods. The characteristic parameters include the amplitude, phase, frequency components, or spectral distribution of the magnetic field noise.

[0032] Specifically, when reconstructing the characteristic parameters of magnetic field noise, a spectral analysis method is used. Frequency domain analysis is performed on the measurement data sequence containing time information to extract the spectral characteristics of the magnetic field noise, enabling real-time reconstruction of its characteristic parameters. Alternatively, a model estimation method can be used. A parameterized physical model is constructed based on the dynamic characteristics of the magnetic field noise, and Bayesian estimation, recursive filtering, or adaptive filtering methods are applied in conjunction with the measurement results to reconstruct the characteristic parameters of the magnetic field noise in real time. These different reconstruction methods can be selected or combined according to specific application requirements.

[0033] Specifically, after obtaining the measurement results, the amplitude, phase, and time-varying characteristics of the magnetic field noise are estimated as characteristic parameters. For example, a physical model based on magnetic field noise can be used to perform overall analysis and parameter estimation of all measurement results obtained in a measurement time series, thereby obtaining the amplitude and phase information of the main frequency components of the magnetic field noise within that time series. The estimation results can be used to generate the compensation signal required for the next measurement time series, realizing cross-time series magnetic field noise feedforward compensation. Alternatively, based on Bayesian estimation methods or data-driven models, the characteristic parameters of the magnetic field noise can be dynamically estimated online. By constructing a probabilistic model between the measurement results and the characteristic parameters of the magnetic field noise, the amplitude and phase estimates of the magnetic field noise are continuously updated based on the real-time quantum measurement results during the operation of a single measurement time series, and the estimation results are directly applied to the compensation control in the current measurement time series, thereby realizing real-time prediction and phase compensation within the time series.

[0034] Furthermore, magnetic field noise can also be predicted using machine learning models. These models can be trained on training data generated from theoretical models or historical measurement data to predict the evolution trend of magnetic field noise over future time periods based on current or historical measurement results.

[0035] When focusing on low-frequency magnetic field noise components, a Ramsey interference sequence is applied to the qubit. The bright and dark states obtained from each measurement, as well as the time interval between adjacent measurements, are recorded, with the interval between adjacent measurements remaining consistent. By statistically analyzing the changes in the measurement results over time, information on the phase evolution caused by low-frequency magnetic field noise can be obtained.

[0036] When focusing on mid-to-high frequency or narrowband magnetic field noise components, a dynamic decoupling timing sequence containing multiple π pulses, such as the CPMG or XY8 timing sequence, is applied to the qubits. By adjusting the pulse interval τ and the number of timing repetitions, the measurement timing sequence can be made sensitive to magnetic field noise within a specific frequency range. By recording the measurement results after the dynamic decoupling timing sequence is executed, and combining the measurement timing parameters, a discrete Fourier transform or equivalent frequency domain analysis is performed on the obtained measurement data, thereby reconstructing the narrowband spectral components of the magnetic field noise.

[0037] According to an embodiment of the present invention, based on the characteristic parameters of the reconstructed magnetic field noise, corresponding compensation information is calculated and generated, such as compensation magnetic field signal or phase compensation amount.

[0038] According to embodiments of the present invention, when compensating for magnetic field noise with time-varying characteristics, a phase compensation method based on quantum manipulation pulse parameter adjustment or an opposite magnetic field compensation method is adopted.

[0039] Specifically, compensation information is applied to the magnetic field compensation device or quantum manipulation pulse parameters to compensate for magnetic field noise. For example, a phase compensation method based on quantum manipulation pulse parameter adjustment includes: calculating the phase accumulation caused by magnetic field noise in the measurement sequence; and adjusting the phase and / or rotation angle in the quantum manipulation pulse parameters based on the phase accumulation. Alternatively, when using an opposite magnetic field compensation method, a compensation magnetic field opposite to the magnetic field noise is generated by controlling the magnetic field compensation device. The magnetic field compensation device includes a single-axis Helmholtz coil structure, and the direction of the compensation magnetic field is along the quantization axis to compensate for magnetic field noise in the quantization axis direction. The above two compensation methods can be used independently or in combination.

[0040] The process then loops back to step S1 to execute the next round of magnetic field noise reconstruction and compensation. The compensation information can be updated between adjacent measurement cycles, allowing the magnetic field noise compensation process to adapt to the time-varying characteristics of the ambient magnetic field and achieve a stable and continuous magnetic field noise suppression effect. The period of the above closed-loop cycle can be set according to the rate of change of the magnetic field noise, with a typical time scale ranging from milliseconds to seconds.

[0041] According to another embodiment of the present invention, a magnetic field noise reconstruction and compensation device based on in-situ measurement of a quantum system is also provided, such as... Figure 2 As shown, the magnetic field noise reconstruction and compensation device includes a quantum system, a data acquisition module, a parameter reconstruction module, a compensation generation module, and a compensation execution module.

[0042] In this system, the quantum system is configured to perform a predetermined sequence of measurements to measure the quantum state;

[0043] The data acquisition module is configured to acquire measurement results of quantum state evolution under the influence of magnetic field noise;

[0044] The parameter reconstruction module is configured to reconstruct the characteristic parameters of the magnetic field noise in real time based on the measurement results;

[0045] The compensation generation module is configured to generate compensation information based on feature parameters;

[0046] The compensation execution module is configured to compensate for time-varying magnetic field noise based on compensation information.

[0047] According to an embodiment of the present invention, during measurement, the response of a single qubit in the quantum system to changes in the magnetic field is based on the measurement. By applying a predetermined measurement sequence to the quantum system, the quantum state accumulates phase changes caused by magnetic field noise during its evolution, which are then reflected in discrete measurement results during the measurement phase.

[0048] The specific forms of measurement sequences include, but are not limited to:

[0049] Ramsey interferometry sequence: suitable for measuring low-frequency magnetic field noise, the measurement sensitivity is adjusted by the time interval between two π / 2 pulses;

[0050] Spin echo sequences: suitable for eliminating the effects of static magnetic field inhomogeneities and measuring dynamic magnetic field noise;

[0051] Dynamic decoupling sequences (e.g., CPMG sequences or XY8 sequences): suitable for measuring mid-to-high frequency or narrowband magnetic field noise, achieving selective sensitivity to noise in specific frequency bands through a specific arrangement of multiple π pulses.

[0052] Each measurement result is associated with a corresponding measurement time, thus forming a measurement data sequence containing time information. This measurement data sequence reflects the variation characteristics of magnetic field noise over time, providing a basis for subsequent reconstruction of magnetic field noise characteristic parameters.

[0053] Quantum systems can be ion trap systems, neutral atom systems, color centers (e.g., NV centers), superconducting qubits, and other quantum systems with single qubits as their basic building blocks; measurement results can be expressed as the occupancy of quantum states among different eigenstates (e.g., the bright / dark state count obtained by fluorescence detection).

[0054] When reconstructing the characteristic parameters of magnetic field noise, the reconstruction method is not limited to a single implementation form. Different analysis and estimation schemes can be selected according to experimental conditions, noise characteristics and application requirements, or multiple schemes can be combined.

[0055] For example, a reconstruction method based on spectral analysis can be used to reconstruct the characteristic parameters of magnetic field noise: frequency domain analysis is performed on the measurement result sequence containing time information to extract the characteristics of magnetic field noise at different frequency components. This method is suitable for the identification and characterization of periodic or narrowband magnetic field noise components (such as 50Hz / 60Hz mains frequencies and their harmonics).

[0056] For example, the characteristic parameters of reconstructed magnetic field noise can be estimated using model- or data-driven methods: based on the physical model and statistical inference methods of the magnetic field noise, the measurement results are analyzed to estimate the phase, amplitude, and time-varying characteristics of the magnetic field noise. A corresponding parameterized model can be constructed based on the dynamic characteristics of the magnetic field noise, and combined with the measurement results, for example, the following statistical inference methods can be used to update and estimate the characteristic parameters of the magnetic field noise:

[0057] Bayesian estimation method: Calculate the posterior probability distribution of magnetic field noise characteristic parameters based on prior probabilities and measurement likelihood functions;

[0058] Recursive filtering methods, such as Kalman filtering and particle filtering, use recursive formulas to achieve real-time parameter updates.

[0059] Adaptive filtering method: The filtering parameters are adaptively adjusted based on the statistical characteristics of the measurement results.

[0060] In addition, data-driven models can be introduced to analyze the measurement results. These models can be trained using pre-built training data to predict magnetic field noise characteristic parameters or their evolution trends from the measurement results. The training data can be generated based on theoretical models of magnetic field noise or derived from historical actual measurement data. Data-driven models (such as neural networks and support vector machines) can supplement or replace the aforementioned model-based statistical estimation methods, improving the flexibility and adaptability of parameter estimation.

[0061] Based on the reconstructed or predicted magnetic field noise characteristic parameters, corresponding compensation information is generated. When compensating for time-varying magnetic field noise based on this compensation information, the compensation information is applied to the quantum system to counteract the influence of magnetic field noise on quantum state evolution. The compensation method can be selected according to the specific system structure and experimental requirements.

[0062] For example, a compensation method based on a magnetic field compensation device can be used: the compensation information is converted into a driving signal to control the magnetic field compensation device to generate a compensation magnetic field that is opposite to the ambient magnetic field noise, thereby reducing the amplitude of the magnetic field noise in the region where the quantum system is located.

[0063] A magnetic field compensation device may include compensation coils and their driving circuits. The compensation coils may be arranged using a Helmholtz coil structure, corresponding to the X, Y, and Z spatial coordinate systems respectively, to achieve independent compensation for magnetic field noise in any direction in three-dimensional space. The compensation coils can be used to compensate for slowly changing magnetic field drift (via DC or low-frequency drive signals) and periodic magnetic field noise components (via AC drive signals).

[0064] The dynamic response requirements of the compensation magnetic field are determined by the bandwidth of the drive circuit and the inductance characteristics of the coil. Typically, the bandwidth of the compensation system should cover the main frequency range of the magnetic field noise to be compensated (e.g., 0.1Hz to 1kHz) to ensure the real-time performance and effectiveness of the compensation.

[0065] For example, a phase compensation method based on quantum manipulation parameters can be used: based on the reconstruction results of magnetic field noise characteristic parameters, the phase accumulation caused by magnetic field noise in the measurement sequence is calculated, and the phase accumulation is compensated by adjusting the quantum manipulation parameters, thereby reducing the influence of magnetic field noise on the coherence of quantum states.

[0066] Specifically, the adjustment of quantum manipulation parameters includes, but is not limited to:

[0067] Pulse phase adjustment: In the Ramsey interferometry sequence, the opposite value of the predicted cumulative phase is added to the phase setting of the second π / 2 pulse;

[0068] Rotation angle adjustment: In spin echo or dynamic decoupling sequences, the rotation angle of the π pulse is adjusted according to the noise amplitude to partially offset the noise effect.

[0069] This method is suitable for situations where the magnetic field noise amplitude is small and the quantum state evolution is mainly affected by phase accumulation. It offers advantages such as fast response speed and no need for additional hardware. Compared to the aforementioned magnetic field compensation methods, phase compensation is more suitable for rapid compensation of high-frequency magnetic field noise, while the magnetic field compensation method is more suitable for suppressing low-frequency magnetic field drift. In practical applications, the two methods can be used in combination to cover a wider frequency range.

[0070] In practical applications, the magnetic field noise reconstruction and compensation method and apparatus of this invention are executed cyclically according to the process of measurement → reconstruction → compensation → remeasurement. Compensation information can be updated between adjacent measurement cycles, enabling the magnetic field noise compensation process to adapt to the time-varying characteristics of the ambient magnetic field, thereby achieving a stable and continuous magnetic field noise suppression effect. The closed-loop cycle period can be set according to the rate of change of the magnetic field noise, with a typical timescale range of 1 millisecond to 10 seconds. For rapidly changing magnetic field noise, a shorter cycle period (e.g., on the order of milliseconds) can be used to achieve rapid tracking; for slowly drifting magnetic fields, a longer cycle period (e.g., on the order of seconds) can be used to improve measurement resolution.

[0071] When the rate of change of magnetic field noise is within the tracking bandwidth, the closed loop can converge to a steady state, achieving effective noise suppression. The selection of the compensation gain should balance response speed and stability; excessive gain may cause system oscillation, while insufficient gain will reduce the compensation effect. Typically, the optimal compensation gain can be determined through experimental debugging or adaptive algorithms. Compared with existing magnetic field stabilization and compensation techniques, the magnetic field noise reconstruction and compensation method and device based on in-situ measurement of quantum systems of this invention reconstructs and compensates environmental magnetic field noise in situ based on the measurement results of a single qubit in a quantum system, introducing new technologies in terms of measurement, compensation, and applicable conditions. It does not rely on external magnetic field detection devices and has low requirements for the initial magnetic field conditions of the experimental setup, enabling effective suppression of magnetic field noise in complex experimental environments, thus including the following advantages and beneficial effects:

[0072] (1) Achieve in-situ measurement of magnetic field noise, avoiding spatial deviation and reducing environmental dependence. By directly utilizing the measurement results of atoms in the quantum system, magnetic field noise information can be obtained without relying on high-performance magnetic shielding structures, low-noise initial magnetic field environments, or external magnetic field detection devices. Since the measurement is based on the actual magnetic field changes felt by the qubits, spatial deviations introduced by the inconsistency between the detection position and the position of the quantum system are avoided, making the magnetic field measurement and compensation process closer to the actual working state of the quantum system. It can be implemented in the presence of large environmental noise or unsatisfactory magnetic field conditions, significantly reducing the requirements for the initial state of the quantum experimental device and the stability of the experimental environment, and improving the practicality and applicability of the magnetic field noise compensation scheme.

[0073] (2) It possesses spectrum reconstruction capabilities, effectively characterizing narrowband and periodic magnetic field noise. By correlating quantum measurement results with time information, the magnetic field noise reconstruction and compensation method and device based on in-situ quantum system measurement of this invention can reconstruct the frequency characteristics of environmental magnetic field noise, and is particularly suitable for identifying and characterizing periodic or narrowband magnetic field noise components (such as 50Hz / 60Hz mains frequency and its harmonics) introduced by power systems and electrical equipment. Through frequency domain analysis or model estimation, the frequency, amplitude, and phase information of the noise can be obtained, providing a basis for subsequent accurate compensation of magnetic field noise.

[0074] (3) Provides a flexible compensation mechanism to adapt to different quantum experimental platforms. It can be achieved by generating a canceling magnetic field (e.g., through a single-axis or triaxial Helmholtz compensation coil), or by adjusting quantum manipulation parameters (e.g., pulse phase, rotation angle) to compensate for phase accumulation caused by magnetic field noise. The compensation method is highly flexible and easy to implement and expand in different types of quantum experimental platforms such as ion traps, neutral atoms, color centers, and superconducting qubits. Different compensation methods can be combined according to the frequency characteristics of magnetic field noise to cover a wide frequency range from DC drift to kilohertz AC noise.

[0075] (4) Significantly improve the coherence performance and operational stability of quantum systems. Through continuous in-situ reconstruction and compensation of magnetic field noise, the influence of magnetic field noise on the quantum state evolution process can be effectively reduced. The reduction in qubit coherence time caused by magnetic field noise can be improved from the original 30%-50% to less than 10%, thereby improving the coherence performance and operational stability of quantum systems under actual operating conditions, and providing a more reliable experimental basis for quantum information processing and quantum precision measurement tasks.

[0076] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reconstructing and compensating magnetic field noise based on in-situ measurements of quantum systems, characterized in that, include: S1: Execute a predetermined sequence of measurements based on the quantum system to measure the quantum state; S2: Obtain the measurement results of quantum state evolution under the influence of magnetic field noise; S3: Reconstruct the characteristic parameters of the magnetic field noise in real time based on the measurement results; S4: Generate compensation information based on the feature parameters; S5: Compensate for the time-varying magnetic field noise based on the compensation information.

2. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 1, characterized in that, When reconstructing the characteristic parameters of magnetic field noise, spectral analysis or model estimation methods are used. The characteristic parameters include the amplitude, phase, frequency components, or spectral distribution of the magnetic field noise.

3. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 2, characterized in that, When reconstructing the characteristic parameters of magnetic field noise, a spectral analysis method is used to perform frequency domain analysis on the measurement data sequence containing time information in order to extract the spectral characteristics of magnetic field noise and realize the real-time reconstruction of the characteristic parameters of magnetic field noise.

4. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 2, characterized in that, When reconstructing the characteristic parameters of magnetic field noise, a model estimation method is used. A parameterized physical model is constructed based on the dynamic characteristics of magnetic field noise, and Bayesian estimation, recursive filtering or adaptive filtering methods are used to reconstruct the characteristic parameters of magnetic field noise in real time in combination with the measurement results.

5. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 1, characterized in that, When compensating for magnetic field noise with time-varying characteristics, a phase compensation method based on quantum manipulation pulse parameter adjustment or an opposite magnetic field compensation method can be used.

6. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 5, characterized in that, Phase compensation methods based on quantum manipulation of pulse parameters include: Calculate the phase accumulation caused by magnetic field noise in the measurement sequence; The phase and / or rotation angle in the quantum manipulation pulse parameters are adjusted based on the phase accumulation.

7. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 5, characterized in that, When using the opposite magnetic field compensation method, a compensation magnetic field opposite to the magnetic field noise is generated by controlling the magnetic field compensation device. The magnetic field compensation device includes a single-axis Helmholtz coil structure, and the direction of the compensation magnetic field is along the quantization axis to achieve compensation for the magnetic field noise in the quantization axis direction.

8. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 1, characterized in that, The quantum system is an ion trap system, a neutral atom system, a color center system, or a superconducting quantum bit system.

9. The method for magnetic field noise reconstruction and compensation based on in-situ measurement of quantum systems according to claim 1, characterized in that, The measurement sequence includes a Ramsey interferometry sequence, a spin echo sequence, or a dynamic decoupling sequence; the measurement result is a measurement data sequence containing time information.

10. A magnetic field noise reconstruction and compensation device based on in-situ measurement of a quantum system, characterized in that, include: A quantum system is configured to perform a predetermined sequence of measurements to measure a quantum state; The data acquisition module is configured to acquire measurement results of quantum state evolution under the influence of magnetic field noise. The parameter reconstruction module is configured to reconstruct the characteristic parameters of the magnetic field noise in real time based on the measurement results. The compensation generation module is configured to generate compensation information based on the feature parameters; The compensation execution module is configured to compensate for magnetic field noise with time-varying characteristics based on the compensation information.

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